1. Field of the Invention
The present invention relates to a display apparatus including a plurality of light emitting device groups, where each of the groups includes a plurality of light emitting devices emitting lights different in color from each other. For example, the present invention relates to a display apparatus including a plurality of light emitting device groups, where each of the groups includes a plurality of organic light emitting devices.
2. Description of the Related Art
The organic light emitting device ((organic electroluminescence device) hereinafter often referred to as a “device”) is now being studied and developed. The above-described organic light emitting device includes a pair of electrodes including an anode and a cathode, and a plurality of organic compound layers including a light emitting layer, which is provided or located between the pair of electrodes. Each of the organic compound layers has a thickness of about a several tens of nm, and a reflection plane including a layer such as an electrode is provided or located on each of both sides of the organic compound layer. When the reflection planes are provided, the optical interference effect, which means that light with a predetermined wavelength is vibrated and intensified inside the organic light emitting device, becomes noticeable. The light intensification achieved through the optical interference has been used to increase the color purity of light emitted from the organic light emitting device.
According to an organic electroluminescent element disclosed in United States Patent Application No. 20050099113, the optical path between the first electrode and a translucent reflection layer is set so that the peak wavelength of a spectrum for extraction satisfies the vibration condition for each of emitted light colors including red, green, and blue (refer to paragraphs [0019] to [0025]).
The above-described wavelength intensified through the optical interference (vibration wavelength) is determined based on the optical path between the plurality of reflection planes. However, when an angle in which the device is visually recognized (view angle) is increased, a vibration wavelength λ is shifted to the short-wavelength side. In that case, the hue of the light emitting device is changed.
When the display apparatus is configured by using the above-described light emitting devices emitting lights with different colors as pixels, the hue of each of the pixels is changed when the pixels are viewed from a slanting direction so that the balance of the color mixture is also changed. Namely, a light emitting device showing a red color at the front shows an orange color depending on the view angle, a light emitting device showing a green color at the front shows a blue color depending on the view angle, and a light emitting device showing a blue color at the front shows a deep blue color depending on the view angle. Consequently, the hue of a white color which is expressed by the mixture of the red color, the green color, and the blue color (white balance) is lost. Since the white color is used to express the skin of a person, the misregistration of the white color, which is caused based on the view angle, deteriorates the display quality of the display apparatus.
Accordingly, a technology for handling the above-described problem is disclosed in United States Patent Application No. 20030034938. A display device disclosed in United States Patent Application No. 20030034938 reduces the white color misregistration occurring when the view angle is large by displacing the peak wavelength of the internal light emitting spectrum of a light emitting layer and that of a multiple interference filter spectrum obtained through a vibration part from each other. More specifically, the peak wavelength of the multiple interference filter spectrum is displaced by as much as +10 nm for a red-color device, +4 nm for a green-color device, and −10 nm for a blue-color device with respect to the peak wavelength of the internal light emitting spectrum so that the value of the white color misregistration becomes Δuv=0.015 or less at a view angle of 60 degrees (refer to paragraphs [0008] to [0009]).
However, even though the display device disclosed in United States Patent Application No. 20030034938 can reduce the white color misregistration occurring due to the view angle, the display device should be designed in consideration of the white color misregistration. Therefore, the purity of the colors of emitted light is often decreased due to the selection of light emitting materials. In that case, the color reproducing range is decreased so that the display property of the display apparatus is compromised.
On the other hand, when the purity of the colors of emitted light is increased to obtain a display apparatus having a wide color reproducing range, as is the case with the light emitting device disclosed in United States Patent Application No. 20050099113, the above-described misregistration of the color mixture (e.g., the white color) caused by the view angle occurs.
Therefore, the result of verifications of the color misregistration caused by the view angle, the verifications being performed by the inventors of the present invention, shows that color misregistration from the white color toward the yellow direction is highly tolerable for an observer.